@article{Mytrochenko_2020, title={Effect of temperature on meiosis in Scots pine plus trees with meiotic mutations and chromosome rearrangements in their genomes}, url={http://forestry-forestmelioration.org.ua/index.php/journal/article/view/258}, DOI={10.33220/1026-3365.136.2020.58}, abstractNote={<p lang="en-US" align="justify"><strong>Introduction</strong></p> <p align="justify"><span lang="en-US">The global </span><span lang="en-US">climate warming</span> <span lang="en-US">can affect the vegetative growth and generative development of pine forests to the south of 54°</span> <span lang="en-US">N. lat. </span><span lang="en-GB">(</span><span lang="en-US">Reich</span><span lang="en-GB"> & </span><span lang="en-US">Oleksyn</span><span lang="en-GB">. </span><span lang="en-US">2008). The generative sphere of Scots pine </span><span lang="en-GB">(</span><span lang="en-GB"><em>Pinu</em></span><span lang="en-US"><em>s</em></span> <span lang="en-US"><em>silv</em></span><span lang="en-GB"><em>estris L</em></span><span lang="en-GB">.)</span><span lang="en-US"> is most </span><span lang="en-US">temperature-</span><span lang="en-US">sensitive, </span><span lang="en-US">especially the meiosis of microsporogenesis. A higher temperature has low mutagenic effect; however it can strengthen effect of other mutagens such as ionizing radiation, ultraviolet rays, and chemicals. For example, a temperature raise brought about an increased </span><span lang="en-GB">frequency</span><span lang="en-US"> of chromosomal aberrations</span><span lang="en-GB"> in meiosis</span><span lang="en-US"> of microsporogenesis in pine trees in contaminated areas after the Chernobil accident </span><span lang="en-GB">(</span><span lang="en-US">Mytrochenko</span><span lang="en-GB"> & </span><span lang="en-US">Shlonchak</span><span lang="en-GB"> 2004).</span><span lang="en-US"> Apart from</span><span lang="en-US"> external mutagens, a</span> <span lang="en-US">Scots pine has genetic factors that cause aberrations</span><span lang="en-GB"> at meiosis</span> <span lang="en-US">of micro- and macro</span><span lang="en-US">sporogenesis:</span><span lang="en-US"> meiotic gene mutations and chromosomal rearrangements. In some</span> <span lang="en-US">Ukrainian</span> <span lang="en-GB">regions, up to 28% of </span><span lang="en-US">Scots pine plus trees </span><span lang="en-US">contain </span><span lang="en-US">these</span><span lang="en-US"> genetic factors</span><span lang="en-GB"> in genomes</span> <span lang="en-GB">(</span><span lang="en-US">Mytrochenko</span><span lang="en-GB"> 2004, 2006). </span></p> <p align="justify"><span lang="en-US"><em>The aim of the study</em></span><span lang="en-US"> was to investigate how temperature influences the frequency</span> <span lang="en-US">of</span><span lang="en-US"> typical aberrations</span><span lang="en-GB"> in meiosis</span> <span lang="en-US">in Scots pine plus trees with meiotic mutations and chromosomal rearrangements.</span></p> <p align="justify"><span lang="en-US"><strong>Materials and Methods</strong></span></p> <p align="justify"><span lang="en-US">The study was carried out in the year 2003</span><span lang="uk-UA"> (</span><span lang="en-US">with the average daily temperature during meiotic divisions (</span><span lang="en-GB">1–7 </span><span lang="en-US">May) of </span><span lang="en-GB">15.8</span><span lang="en-US">°</span>С<span lang="en-US">) and in the year 2004 </span><span lang="uk-UA">(</span><span lang="en-US">with the average daily temperature during meiotic divisions (</span><span lang="en-GB">23</span><span lang="en-US">–</span><span lang="en-GB">30 April) of</span> <span lang="en-GB">10.8</span><span lang="en-US">°</span>С<span lang="en-US">). Fourteen clones of plus trees with a different meiotic mutations and chromosomal rearrangements were selected in the S</span><span lang="en-GB">cots pine clone bank</span> <span lang="en-GB">located in</span> <span lang="en-US">the</span> <span lang="en-US">Staropetrivske Forestry in the State Enterprise “Kyiv Forest Research Station”</span><span lang="uk-UA">.</span></p> <p class="western" lang="uk-UA" align="justify"><span lang="en-US">The meiotic gene mutations were</span> <span lang="en-US"><em>ps</em></span> + <span lang="en-US"><em>tps</em></span> <span lang="en-US">(1</span><span lang="en-GB"> clone)</span><span lang="en-US">, </span><span lang="en-US"><em>ms</em></span><em>43</em> <span lang="en-US">(3</span><span lang="en-GB"> clones</span><span lang="en-US">)</span>, <span lang="en-US"><em>ds</em></span><em> І</em> <span lang="en-US">(2</span><span lang="en-GB"> clones</span><span lang="en-US">),</span> <span lang="en-US"><em>ds </em></span><em>ІІ</em> <span lang="en-US">(2 </span><span lang="en-GB">clones</span><span lang="en-US">).</span> <span lang="en-US">The chromosomal</span> <span lang="en-US">rearrangements were:</span><span lang="en-GB"> inversion </span>(In) –<span lang="en-US"> 5</span><span lang="en-GB"> clones</span><span lang="en-US"> and</span><span lang="en-GB"> translocation </span>(Tr)<span lang="en-US"> </span>–<span lang="en-US"> 1</span><span lang="en-GB"> clone</span><span lang="en-US">.</span></p> <p align="justify"><span lang="en-US">During the meiotic divisions, </span><span lang="en-US">microstrobiles </span><span lang="en-US">from the each clone were collected every day and fixed in 3:1 ethyl alcohol-acetic acid for 24 hours and then stored in 70% ethyl alcohol in a refrigerator. The meiotic divisions</span> <span lang="en-US">were studied in a temporary squash preparations stained in hematoxylin according to the methods of </span><span lang="en-GB">Shoferystova </span><span lang="en-US">(</span><span lang="en-GB">1973). The s</span><span lang="en-US">lides were examined with the </span><span lang="en-GB">“Biorex-2”</span><span lang="en-US"> microscope</span> <span lang="en-US">with a magnifying power of 40 ? 15 and 40?7; microphotography was done with the </span><span lang="uk-UA">Cаnon A310</span><span lang="en-US"> camera.</span></p> <p align="justify"><span lang="en-US">We studied 500 </span><span lang="en-US">microsporocytes for ana-telophase in both</span><span lang="en-US"> meiotic divisions. Among them, a percentage of</span><span lang="en-US"> microsporocytes</span><span lang="en-US"> with</span><span lang="en-US"> typical aberrations for</span><span lang="en-US"> each meiotic mutation and chromosomal rearrangement were determined.</span> <span lang="en-US">A</span> <span lang="en-US">difference</span> <span lang="en-US">in parts of</span> <span lang="en-US">microsporocytes</span><span lang="en-US"> with deviations was</span> <span lang="en-US">determined</span><span lang="en-US"> by </span><span lang="en-US"><em>t</em></span><span lang="uk-UA">-</span><span lang="en-US">criterion</span><span lang="uk-UA"> (Lakin 1990</span><span lang="en-US">)</span></p> <p lang="en-US" align="justify"><strong>Results</strong></p> <p align="justify"><span lang="en-US"><em><strong>Meiotic gene mutations.</strong></em></span> <span lang="en-US">Mutations </span><span lang="en-US"><em>ps</em></span> <span lang="en-GB">+ </span><span lang="en-US"><em>tps</em></span><span lang="en-GB"> and </span><span lang="en-US"><em>ms</em></span><span lang="en-GB"><em>43</em></span><span lang="en-GB"> disturb a structure and function of the spindle apparatus in the</span><span lang="en-US"> meiotic cells. Both mutations are monogenic and recessive, they occur in </span><span lang="en-US">microsporogenesis</span><span lang="en-US"> only.</span></p> <p align="justify"><span lang="en-US"><em>Mutation ps</em></span><span lang="en-GB"><em>+ </em></span><span lang="en-US"><em>tps</em></span> <span lang="en-GB">involves formation of two pollen</span><span lang="en-US"> grains and a parallel </span><span lang="en-GB">spindles</span><span lang="en-US"> orientation at the second meiotic division with their following fusion on both ends (</span><span lang="en-US"><em>ps</em></span><span lang="en-GB">)</span><span lang="en-US"> or one end (</span><span lang="en-US"><em>tps</em></span><span lang="en-GB">)</span><span lang="en-US">. </span><span lang="en-GB">The spindle</span><span lang="en-US"> fusion was observed in 4.4% of</span><span lang="en-US"> microsporocytes in warm 2003 only.</span></p> <p align="justify"><span lang="en-US">Cytologic picture of mutation</span><span lang="en-US"><em> ms</em></span><span lang="en-GB"><em>43</em></span><span lang="en-GB"> was evident as</span><span lang="en-US"> randomly scattered chromosomes in a cell or uneven distribution among several poles in cause of </span><span lang="en-GB">spindle splitting at A I, with further formation of polyad</span><span lang="en-US">s</span><span lang="en-GB"> instead of dyads and tetrads. The</span><span lang="en-US"> average</span><span lang="en-GB"> percentage of </span><span lang="en-US">microsporocytes</span><span lang="en-US"> with</span><span lang="en-US"> typical for </span><span lang="en-US"><em>ms</em></span><span lang="en-GB"><em>43</em></span> <span lang="en-US">aberrations </span><span lang="en-GB">was 5.1% in </span><span lang="en-US">warm</span><span lang="en-GB"> 2003 and 4.3% in cold 2004. However, the study did not show a significant</span> <span lang="en-US">difference</span> <span lang="en-US">between them</span><span lang="en-US"> by </span><span lang="en-US"><em>t</em></span><span lang="uk-UA">-</span><span lang="en-US">criterion.</span> <span lang="en-US">The mutation has a photoperiodic sensitivity (Peremyslova</span><span lang="en-GB"> 2006).</span></p> <p align="justify"><span lang="en-US"><em>Desynaptic mutations</em></span> <span lang="en-US"><em>ds</em></span><span lang="en-GB"> disturb the chiasmata formation as a result </span><span lang="en-US">of </span><span lang="en-GB">untimely synaptonemal complexes destruction leading to the appearance the univalents in M I and </span><span lang="en-US">chromosome lagging in A I-II.</span> <span lang="en-US">Desynaptic mutations are divided into two groups (</span><span lang="en-US"><em>ds </em></span><em>І</em><span lang="en-GB"> and </span><span lang="en-US"><em>ds </em></span><em>ІІ</em><span lang="en-US">) by the ability of centromeres of sister chromatid to separate at A I (</span><span lang="en-US"><em>ds</em></span> <em>ІІ</em><span lang="en-US">) or not separate (</span><span lang="en-US"><em>ds</em></span> <em>І</em><span lang="en-US">).</span><span lang="en-GB"> The </span><span lang="en-US">mutations are monogenic and recessive; at that, they occur in </span><span lang="en-US">macro- and</span> <span lang="en-US">microsporogenesis</span><span lang="en-US">. Both the </span><span lang="en-US"><em>ds</em></span> <em>І</em><span lang="en-US"> and the </span><span lang="en-US"><em>ds</em></span> <em>ІІ</em><span lang="en-US"> are </span><span lang="en-US">temperature-</span><span lang="en-US">sensitive. On the average, </span><span lang="en-US">in </span><span lang="en-US"><em>ds</em></span> <em>І</em><span lang="en-US"> mutants,</span><span lang="en-GB"> the proportion of the</span><span lang="en-US"> microsporocytes</span><span lang="en-US"> with lagging chromosomes </span><span lang="en-GB">was </span><span lang="en-US">5.6%</span><span lang="en-GB"> in </span><span lang="en-US">warm</span><span lang="en-GB"> 2003</span> <span lang="en-GB">and in only 2.3% in cold 2004.</span><span lang="en-US"> On the contrary, </span><span lang="en-US">in </span><span lang="en-US"><em>ds</em></span> <em>І</em><span lang="en-US"><em>I</em></span><span lang="en-US"> mutants, 4.7% of the </span><span lang="en-US">microsporocytes</span><span lang="en-US"> with lagging chromosomes </span><span lang="en-GB">were found</span><span lang="en-US"> in </span><span lang="en-GB">cold 2004 and 1.4% in </span><span lang="en-US">warm </span><span lang="en-GB">2003. </span><span lang="en-US">The difference</span> <span lang="en-US">between the yearly</span> <span lang="en-US">average</span><span lang="en-GB"> percentages of the </span><span lang="en-US">aberrant microsporocytes</span><span lang="en-US"> was</span> <span lang="en-US">reliable for</span> <span lang="en-US"><em>t</em></span><span lang="uk-UA">-</span><span lang="en-US">criterion with the 5% of confidence level for the both mutations.</span></p> <p align="justify"><span lang="en-US"><em><strong>The chromosomal rearrangements.</strong></em></span> <span lang="en-US"><em>Inversions</em></span><span lang="en-US">. At meioses we can observe only large heterozygous paracentric inversions, when there is synapsis of homologous segments resulted from the formation of an inversion loop. Crossing over within the loop produces acentric fragments and chromosome and chromatid bridges, which can be observed in A I-II. In clones with inversions, 11.4%</span><span lang="en-US"> of the aberrant microsporocytes</span><span lang="en-GB"> were found in 2003 and only 3.7% in 2004.</span></p> <p align="justify"><span lang="en-GB"><em>Translocation </em></span><span lang="en-GB">is a mutual exchange of terminal segments from the arms of two</span><span lang="en-US"> non-homologous</span><span lang="en-GB"> chromosomes. At meiosis, when a </span><span lang="en-US">heterozygous </span><span lang="en-GB">translocation is present, during pairing of homologous chromosome segments, followed by crossing-over, translocations may form a tetravalent, and </span><span lang="en-US">rings of 4 chromosomes</span><span lang="en-GB"> are</span><span lang="en-US"> formed</span><span lang="en-GB"> at M I</span><span lang="en-US">. </span><span lang="en-US">If </span><span lang="en-US">the</span><span lang="en-GB"> pairing</span><span lang="en-US"> does not take place, </span><span lang="en-GB">there are</span><span lang="en-US"> open bivalents in М I. In</span><span lang="uk-UA"> 2003</span><span lang="en-US">, only open</span> <span lang="en-US">bivalents were noticed while in</span> <span lang="en-US">cold </span><span lang="uk-UA">200</span><span lang="en-US">4,</span> <span lang="en-US">the rings of four chromosomes were </span><span lang="en-US">observed</span><span lang="en-GB"> in 19.2% </span><span lang="en-US">of the </span><span lang="en-US">microsporocytes</span><span lang="en-GB"> studied in metaphase</span><span lang="en-US">.</span> <span lang="en-US">Probably, frequency of</span><span lang="en-GB"> unbalance</span><span lang="en-US"> gametes formation depends on the </span><span lang="en-GB">tetravalent</span><span lang="en-US"> presence</span><span lang="en-GB"> or absence as </span><span lang="en-US">this </span><span lang="en-GB">clone</span> <span lang="en-US">has year-to-year variation </span><span lang="en-US">of underdeveloped pollen grains</span><span lang="en-US"> and seed buds number.</span></p> <p lang="en-US" align="justify"><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><strong>Conclusions</strong></span></span></p> <p lang="en-US" align="justify"><span style="font-family: Verdana, sans-serif;"><span style="font-size: small;"><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">The generative</span></span> <span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">sphere of most studied Scots pine plus trees with the mei-genes mutations and chromosomal rearrangements in their genomes has an increased temperature-sensitivity during meiosis</span></span> <span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">in the process of microsporogenesis.</span></span> </span></span></p> <p lang="en-US" align="justify"><span style="font-family: Verdana, sans-serif;"><span style="font-size: small;"><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">Among the mei-genes mutations which </span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">disturb the structure of the spindle fission (</span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>ps</em></span></span> <span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">+ </span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>tps</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"> and </span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>ms</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"><em>43</em></span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">)</span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"> considerable temperature dependence was detected in </span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>ps</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"> + </span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>tps</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">. A change in the temperature regime did not influence the mеi-gene mutant </span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>ms43</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"> expression.</span></span></span></span></p> <p lang="en-US" align="justify"><span style="font-family: Verdana, sans-serif;"><span style="font-size: small;"><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">The mutant mei-genes that control certain processes of synapsis and recombination (</span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"><em>ds </em></span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>І</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">,</span></span> <span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"><em>ds </em></span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><em>ІІ</em></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">) and chromosomal rearrangements (inversions and translocations) have an increased temperature-sensitivity. At that, the </span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">aberrations</span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"> quantity caused by them </span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">depends on the</span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"> processes of synapsis and recombination.</span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"> In the trees with inversions, the part of aberrant microsporocytes</span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"> increase</span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">d</span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB"> when a</span></span></span> <span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">temperature raised, and in those with t</span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">ranslocation</span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">, the tetravalents formation was observed when temperature decreased. </span></span></span></span></p> <p lang="en-US" align="justify"><span style="font-family: Verdana, sans-serif;"><span style="font-size: small;"><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">A large number of plus trees with the mei-genes mutations and chromosomal rearrangements in their genomes in certain regions suggests an idea that they contain particular genetic factors, which give them an advantage in growth due to their high competitive abilities in optimal conditions or resilience in unfavourable ones. Therefore, these trees can be recommended to use when creating seed orchards. Scots pine plus trees with mei-genes mutations and chromosome rearrangements should be thoroughly studied in</span></span> <span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;"><span lang="en-GB">clone archive </span></span></span><span style="font-family: ’Times New Roman’, serif;"><span style="font-size: medium;">plantations, and their progeny should be actively used in subsequent breeding programmes.</span></span></span></span></p> <p class="western" lang="uk-UA"><span lang="en-GB"><strong>4 Figs., 1 Table, 23 Refs.</strong></span></p> <p align="justify"><span lang="en-US"><strong>Key words:</strong></span><span lang="en-US"> Scots pine,</span><span lang="en-US"> microsporogenesis,</span><span lang="en-GB"> meiosis,</span><span lang="en-US"> meiotic gene mutations, chromosomal rearrangements, temperature sensitivity.</span></p>}, number={136}, journal={Forestry and Forest Melioration}, author={Mytrochenko, V. V.}, year={2020}, month={Jun.}, pages={58–66} }